How Colorblindness Works

Where does colorblindness come from? How does it happen? Like so many things, it's mostly about your genes -- the luck of the draw.

It's true that many more men than women are colorblind. About 8 percent of Caucasian men have red-green color deficiency, compared to .5 percent of women. Colorblindness is less common in African and Asian populations. Achromatopsia, complete colorblindness, affects one in 40,000 people. On the Pingelap islands, however, where marriage to relatives is common, achromatopsia occurs in 5 to10 percent of the population. Tritan defects affect fewer than 1 in 10,000 people around the world.

Red-green colorblindness is sex-linked recessive -- it's carried on the X chromosome. Men have an X and a Y chromosome, so if the X chromosome carries the gene mutation for colorblindness, he's going to be colorblind. Women have two X's, so they'd have to get two copies to make it happen.

Tritanopia isn't sex-linked -- it's an autosomal dominant disorder, but it can also be acquired. Most acquired colorblindness falls under tritanopia. Glaucoma, for instance, can cause blue-yellow colorblindness. Men and women get tritanopia in equal numbers. Complete colorblindness is autosomal recessive.

Some drugs, like digitalis and chloroquine, can even cause colorblindness. So can some industrial chemicals, as well as injuries to the eye.

Here are some diseases and conditions that can cause color vision defects:

Aging also has an effect on color vision. Colors seem to fade as we get older.

Unfortunately, there's no cure for colorblindness. There are some corrective lenses that on the market that claim to help with colors, but they can mess with depth perception and other aspects of visions. With any luck, the future will hold surgical options or perhaps gene therapy, but for now, coping mechanisms are the best bet.